1. Field of the Invention
The invention relates to a device for producing fluid particles, especially producing an aerosol, with a permeable wall having pore-like through channels, a nozzle for applying the spray jet onto the permeable wall, and a device for loading the permeable wall with a compressed gas penetrating the permeable wall while entraining the particle former under formation of the fluid particles.
2. Description of the Related Art
From U.S. Pat. No. 5,549,247, such a device for spraying fragrances is known. In this device the permeable wall is formed by a stopper of wire mesh which is arranged above the stopper in a cylindrical chamber with a mist exit opening. Below the stopper a nozzle that sprays axially into the chamber is provided, wherein the compressed gas flowing through the stopper and the particle former, sucked in by the compressed gas stream from the supply bottle, will flow through the nozzle.
From European patent application 0 119 527 an extinguishing device for extinguishing fires is known. The extinguishing device has a chamber into which a water stream mixed with a foaming medium and an air stream can be guided, wherein the water-air-mixture is forced with foam formation through the sieve limiting the chamber.
The present invention has the object to make a device of the aforementioned kind suitable for further technical applications.
The device solving this object according to the invention is characterized in that a device for adjusting the amount of particle former transported by the spray jet per time unit and/or a device for adjusting the amount of compressed gas passing per time unit through the wall is provided.
Advantageously, such a device can be used, for example, for fluid treatment of sensitive, easily deformable objects, especially for their cooling, or other applications requiring certain metering of the particle formation, for example, in a burner. With the inventive use of a permeable wall having pores, it is possible to produce fluid particles with minimal kinetic energy by the effect of the compressed gas flowing through the permeable wall so that at the exit side of the wall a fluid particle stream with particles having extremely low energy per particle can be produced. With such a particle stream, for example, formed of liquid nitrogen, it is possible to cool and solidify liquid surfaces, without the solidified liquid surface showing deformations resulting from the effect of the stream.
Preferably, the particle former is sprayed onto the pressure-loaded walls such that simultaneously substantially the entire surface area of the permeable wall is wetted.
In one embodiment in which the fluid particles are used for treating deformation-sensitive objects, the permeability of the wall and the gas pressure are selected such that, for a continuous supply of the particle former, a continuous particle stream will exit from the wall with a kinetic energy per particle that is minimal in comparison to the kinetic energy of the spray jet particles. The amount of particle former transported by the spray jet per time unit can be adjusted via the pressure differential of the conveying pressure acting on the particle former and the gas pressure of the compressed gas. Furthermore, the permeable wall could be provided as an exchangeable part so that wall parts with different permeability can be used.
Advantageously, the permeable wall is substantially horizontally arranged and the aerosol former is applied from above onto the wall. In this case, the particle formation is enhanced by gravity. The wall, however, can be arranged in any desirable position and a particle former can also be forced through the wall especially vertically from below in the upward direction.
According to a preferred embodiment of the inventive device, the wall is a bottom wall of a pressure chamber receiving the spray jet and loaded by the compressed gas, wherein the pressure chamber is embodied especially cylindrically and the bottom wall and the spray jet are arranged coaxially to the cylinder axis.
A buffer volume can be arranged upstream of the pressure chamber for compensation of pressure fluctuations of the compressed gas.
Advantageously, the permeability of the permeable wall, the gas pressure, and the amount of particle former applied per time unit onto the wall are selected such that, for a continuous transport of the particle former from the surface of the permeable wall into the wall, the formation of a coherent liquid film of the particle former is prevented. In this manner it is ensured that at the surface of the permeable wall the impinging spray droplets of the particle former will break up into smaller particle units.
The permeable wall has through channels that are especially pore-like, preferably with through widths in the micrometer range (5 to 500 xcexcm, depending on the pressure level).
Sinter discs, for example, especially made of metal, glass, or ceramic, can be used as permeable walls. It is furthermore possible that for producing a directed fluid particle stream a permeable wall is used which is provided with correspondingly oriented through channels.
Especially when using the device for cooling objects, the particle former can be liquid nitrogen and the compressed gas can be gaseous nitrogen.
The invention will be explained and described in more detail with the aid of a particular embodiment and the accompanying drawings relating to this embodiment. It is shown in: